The invention relates to a cell cover comprising current clips for prismatic cells.
An apparatus of this kind is known from document US patent publication no. 2012/148,909 A.
In the text which follows, the invention is described in connection with an electrochemical energy storage cell for a mobile application, in particular as an energy storage device for a drive motor in a motor vehicle; this is not to be understood to be a restriction of the invention to an application of this kind.
High demands are made of the storage density of energy storage cells for mobile applications since the storage density and therefore the weight of the energy store have a great influence on the usability of energy stores of this kind. An energy storage cell has an electrochemically active part in which the energy can be directly stored, so-called cell stack or cell winding, and a passive part. The passive part of the energy store includes, among other things, the housing device and also electrical conductors for supplying and carrying away electrical charge to/from the active part. The increase in the power density of an energy storage cell can be achieved, in particular, by improving the cell chemistry or by reducing the space requirement of the passive part.
US patent publication no. 2012/148,909 A discloses an energy storage cell in which current clips are connected to the cell cover by way of an interlocking connection. To this end, the cell cover has a curved surface into which the current clip can be inserted at its top end.
One object of the invention is to provide an improved cell cover with current clips for a prismatic cell.
A cell cover is designed to receive at least one current clip, but preferentially two current clips, and electrical connections in order to allow electrical contact to be made with the electrochemical storage cell. Within the meaning of the invention, a current clip is understood to be a device which makes electrical contact with a prismatic energy storage cell and conducts current from or to said cell. In particular, an energy storage cell of this kind is designed as a stacked, folded or so-called jellyroll cell and has a square basic outline as compared with a substantially cylindrical storage cell. Cuboidal cells of this kind can, in particular, also be called pouch or coffee bag cells. Cuboidal cells of this kind also include, in particular, cells of this geometric shape with a metal or plastic housing or with a housing which is composed of at least these two materials, so-called hybrid housings.
In connection with this invention, the terms cell stack and cell winding are used in as equivalents since, in particular, the manner of layering of the anodes/cathodes, in particular (layered, stacked or wound) is of secondary importance to the invention.
The current clip can preferably be connected to an electrical connection, wherein the electrical connection is designed to make contact with the storage cell on the outside and, in particular, is designed as a so-called pole of the storage cell. In this case, inner is understood to be relative to the cell stack (anode/cathode layering). This cell stack can be accommodated in a sheathing or a housing and the area surrounding said housing or said sheathing is understood to be the “outside”.
Furthermore, the cell cover has a covering plate with a bottom side and a top side. At least one, but preferably two, of the electrical connections is/are arranged on the top side of the covering plate. In particular one, but preferably two, of the current clips is/are arranged on the bottom side of the covering plate.
This covering plate has a current-carrying recess. The current clip can be connected to the electrical connection on the top side of the covering plate by way of an electrical conductor or an electrically conductive section through said current-carrying recess.
The covering plate has a connection region for connection, in particular for mechanical connection, to the current clip. The current-carrying recess is arranged in said connecting region. The current-carrying recess extends from the bottom side to the top side of the covering plate. According to the invention, the covering plate has at least one connecting recess in addition to the current-carrying recess. Said connecting recess is preferentially arranged at a distance from the current-carrying recess. Further preferentially, at least one of the current clips can be connected in an interlocking manner to the covering plate in the connecting recess.
In this case, an interlocking connection of this kind of the current clip to the covering plate is also understood to be an indirect connection. An indirect connection is preferentially a connection between an intermediate or adaptive piece, so that the current clip cannot make direct contact with the covering plate, at least in sections.
The covering plate further preferentially has an at least substantially planar or flat top side, in particular in the section which is situated opposite the connecting region on the bottom side. The opposite region is preferentially understood to mean that at least the region which is situated directly opposite the bottom side. The distance between the bottom side of the covering plate, at least in the region which directly surrounds the connecting region, and the plane within the connecting region which is designed to directly or indirectly make contact with the current clip is preferably less than double, preferentially less than 1.5 times and preferably less than 1 times the wall thickness of the covering plate in the connecting region.
Within the meaning of the invention, the covering plate is preferably understood to be a thin-walled elongate component. The covering plate is preferentially designed as an, in particular thin-walled, sheet-metal component. The covering plate further preferably contains aluminum or a steel material as a constituent part or is composed of a material of this kind. The installation space requirement in the vertical direction is reduced, in particular, by the covering plate having a planar top side/face in said vertical direction.
The prior art discloses cell covers which, in the connecting region between covering plate and current clip, have a three-dimensional deformation of the covering plate in order to establish an interlocking connection between the current clip and the covering plate. According to the invention, an interlocking connection between the current clip and the covering plate is achieved by a connecting recess, without the covering plate being three-dimensionally deformed for this purpose; in particular, an improved energy storage cell can be achieved in this way.
Within the meaning of the invention, a prismatic cell is understood to be, in particular, a lithium-based energy storage cell, in particular a lithium-ion energy storage cell. Said storage cell is preferentially characterized by its structural shape. In respect of the structural shape, a distinction is made between at least substantially cylindrical rolled storage cells and prismatic folded, layered storage cells and so-called jellyroll cells. The invention preferentially relates to substantially cuboidal or prismatic storage cells.
Within the meaning of the invention, the electrical connections are understood to be the positive pole and the negative pole of the energy storage cell for outputting or receiving the electrical power to/from outside the energy storage cell.
Within the meaning of the invention, the current clip is understood to be a device which firstly makes electrical contact with the prismatic cell and secondly outputs the electrical charge to the electrical connections or receives said electrical charge from said electrical connections. A current clip of this kind further preferentially has at least one conductor arm, but preferably two conductor arms. Said conductor arms are further preferentially designed to make electrical contact with the prismatic cell. The current clip further preferentially has a contact covering face in the direction of the covering plate. The current clip preferentially has a U-shaped cross section in the case of which the conductor arms constitute the limbs of the U and the covering face section connects the two conductor arms to one another. The current clip can rotate in relation to the covering plate, in particular during assembly. This is prevented by the interlocking connection according to the invention between current clip and covering plate.
The current clip is preferentially composed of an aluminum material or contains at least aluminum as a constituent part. A second current clip further preferentially contains copper as a constituent part or is composed of copper. The use of copper and aluminum for the current clips has proven advantageous since said metals firstly are readily electrically conductive and secondly are readily deformable.
In a preferred embodiment, the current clip can be indirectly connected to the covering plate. Within the meaning of the invention, indirect connection of the current clip to the covering plate is understood to mean that the current clip firstly makes contact with an adapter plate, and secondly the adapter plate makes contact with the covering plate. The adapter plate preferentially contains an insulating material as a constituent part or is composed of an electrically insulating material of this kind. Current is preferentially conducted from the current clip to the electrical connection by the electrical conductor which extends through the current-carrying recess. In this case, the electrical conductor can be cohesively connected both to the current clip and also to the electrical connection. The electrical conductor is further preferentially integrally formed with the electrical connection. Creepage currents between the covering plate and the current clip can advantageously be prevented in particular by defining an electrical line by said electrical conductor between the current clip and the electrical connection.
In a preferred embodiment, the covering plate has a wall thickness T in a section in which the connecting region is arranged. The connecting recess has a depth t for receiving the current clip in the covering plate. The depth t is preferably less than the wall thickness T. The connecting recess is preferentially designed as a pocket in the covering plate. A pocket is further preferentially understood to be a recess which does not completely breach the covering plate. A connecting recess can further preferentially be introduced into the covering plate by a deformation process. The strength and the rigidity of the covering plate is only slightly influenced and the current clip can be securely accommodated on the covering plate in particular by a non-continuous connecting recess.
In a preferred embodiment, the covering plate has a wall thickness T in the section in which the connection region is arranged. The recess for receiving the current clip has a depth t. Said depth t is preferentially equal to the wall thickness T. In particular, the connecting recess extends completely through the covering plate on account of the depth t and the wall thickness T being equal. The connecting recess is preferentially designed as an aperture in the covering plate. The connecting recess further preferentially extends from the bottom side to the top side of the covering plate. It is possible to hold the current clip particularly securely on the covering plate in particular through a connecting recess which completely breaches the covering plate.
In a preferred embodiment, the current clip has an electrically insulating coating in the section in which said current clip makes contact with the covering plate or the adapter plate. Said electrically insulating coating can preferentially be cohesively connected to the current clip. An electrically insulating coating of this kind is further preferentially understood to be a coating with a plastic, in particular plastic granules or as a kind of varnishing. Improved electrical insulation between the current clip and covering plate can be achieved in particular by an electrically insulating coating in the contact region between the current clip and the covering plate or between the current clip and the adapter plate.
In a preferred embodiment, at least one of the electrical connections can be connected to the current clip. This electrical connection is further preferentially electrically insulated from the covering plate. An insulating material is further preferentially provided for this electrical insulation between the electrical connection and the covering plate. The electrical connection and the current clip can further preferentially be cohesively connected to one another. The electrical connection further preferentially has an electrical conductor which extends through the current recess of the covering plate and said electrical conductor can preferentially be cohesively connected to the electrical connection or preferably integrally formed with said electrical connection. A plurality of the electrical connections are further preferentially electrically insulated from the covering plate. Creepage currents between the electrical connections and the covering plate can be prevented and the covering plate can be kept free of electrical voltages in particular by the electrical insulation of the electrical connections in relation to the covering plate.
In a preferred embodiment, at least one of the current clips contains copper or a copper alloy as a constituent part or is composed of said materials, and the electrical connection which can be connected to said current clip contains aluminum or an aluminum alloy as a constituent part or is composed of aluminum or an aluminum alloy. The current clip and the electrical connection can preferentially be connected to one another in a cohesive manner or interlocking manner. A cohesive connection is preferentially designed as a weld or solder connection. In particular, the use of a copper/aluminum material mix makes it possible to readily adapt the electrical connection and the current clip to meet the respective requirements. A particularly secure connection of current clip to electrical connection is made possible in particular by an aluminum/aluminum or copper/copper connection.
In a preferred embodiment, the current clip has a contact covering face which is designed to make mechanical contact with the covering plate or the adapter plate. The current clip further has at least one conductor arm which is designed to make electrical contact with the electrochemical storage cell. In this case, the conductor arm makes contact with the electrochemical storage cell preferentially within a conductor section. The current clip extends in particular, starting from the contact covering face, at an angle of at least virtually 90°, or orthogonally to said covering face.
The current clip further preferentially has at least two conductor arms which together with the contact face form, in particular, a U-shaped cross section. A distance K between an end of the conductor section which faces the contact face and the contact covering face is, in particular, ≥1 times the wall thickness L of the current clip in the region of the contact covering face. The distance K is preferentially >2 times L, preferably >3 times L and particularly preferably >4 times L. Furthermore, the distance K is <15 times L, preferentially <12 times L, preferably <10 times L and particularly preferably <8 times L. It has been found that an excessively small distance K can lead to problems when the conductor arm makes contact with the electrochemical storage cell; on the other hand, a large distance K leads to an increased installation space requirement. In particular, selecting the distance K from the described region leads to good contact being made with the electrochemical storage cell by the conductor arm on the one hand and to a low installation space requirement on the other hand.
In a preferred embodiment, the covering plate has a plurality of connecting recesses. The covering plate preferentially has two or more connecting recesses. The connecting recesses are further preferentially symmetrically spaced apart from the current-carrying recess or are arranged symmetrically in relation to said current-carrying recess. The connecting recesses are preferentially arranged in an edge region of the contact face between the current clip and the covering plate or between the covering plate and the adapter plate. Particularly simple mounting of the current clip is made possible in particular by a symmetrical configuration of two or more connecting recesses.
The connecting recesses are further preferentially arranged in an asymmetrical manner. Unambiguous assignment of the current clip (positive/negative pole) to the covering plate is made possible in particular by an asymmetrical arrangement or configuration of the connecting recesses.
In a preferred embodiment, the adapter plate has an adapter recess for receiving the current clip. The adapter plate further preferentially has raised portions or projections opposite the side which contains the adapter recess, said raised portions or projections being designed to engage into the connecting recess on the covering plate.
The adapter recess preferentially has a T-shaped configuration. The adapter recess is preferentially understood to be a recess which extends completely through the adapter plate; the adapter recess is preferably understood to be a recess which does not extend completely through the adapter plate. In particular, a T-shaped configuration of the adapter recess allows firstly secure fixing of the current clip in relation to the adapter plate and secondly unambiguous assignment of the current clip to the adapter plate.
In a preferred embodiment, at least one of the connecting recesses, preferably a plurality of or all of said connecting recesses, extends/extend as far as the edge of the covering plate. In particular, connecting recesses of this kind are understood to be recesses which have an open edge. A connecting recess which has an open edge of this kind therefore preferentially extends from within the covering plate as far as the edge of said covering plate.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.